1. Field of the Invention
The present invention relates to a lithium rechargeable battery having improved corrosion resistance and a method of making the same.
2. Description of the Related Art
In general, unlike a primary battery, a rechargeable battery may be charged and discharged over and over again and may be used as a power source for various small portable electronic devices such as cellular phones, PDAs, notebook computers, and so on. Lithium secondary batteries have, in particular, been widely employed in the latest generation of electronics devices. The lithium secondary battery may have an operating voltage of 3.6 V, which is three times higher operating voltage than Ni—Cd or Ni-MH batteries widely used as power sources of electric-electronic devices. In addition, the lithium secondary battery may exhibit a relatively high energy density per unit weight.
The lithium rechargeable battery generally employs a lithium based oxide as a positive electrode active material and a carbonaceous material as a negative electrode active material. Here, the lithium rechargeable battery may be manufactured in various shapes, e.g., cylindrical can types, rectangular or prismatic can types, pouch types, etc.
A case used for a lithium rechargeable battery is made of a metallic material having excellent processability such as aluminum or iron. The metallic material may be readily affected by external surroundings. In particular, aluminum, which is an amphoteric metal, has highly processable and is widely used in lithium ion rechargeable batteries. However, aluminum is liable to corrosion under acidic and alkali environments, which may generate salts, resulting in a reduction of the weight of the lithium ion rechargeable battery or deterioration in battery characteristics such as a voltage drop.